Polarized light ions and spectator nucleon tagging at EIC

TL;DR

This paper discusses how an Electron-Ion Collider with advanced detection can enable detailed studies of polarized light nuclei, advancing understanding of neutron spin, nuclear structure, and QCD effects through spectator nucleon tagging.

Contribution

It proposes a novel experimental approach using spectator nucleon tagging at EIC to explore nuclear and QCD physics with polarized light nuclei.

Findings

Potential to precisely measure neutron spin structure

Ability to study quark/gluon structure at high x

Exploration of shadowing effects at low x

Abstract

An Electron-Ion Collider (EIC) with suitable forward detection capabilities would enable a unique experimental program of deep-inelastic scattering (DIS) from polarized light nuclei (deuterium 2H, helium 3He) with spectator nucleon tagging. Such measurements promise significant advances in several key areas of nuclear physics and QCD: (a) neutron spin structure, by using polarized deuterium and eliminating nuclear effects through on-shell extrapolation in the spectator proton momentum; (b) quark/gluon structure of the bound nucleon at x > 0.1 and the dynamical mechanisms acting on it, by measuring the spectator momentum dependence of nuclear structure functions; (c) coherent effects in QCD, by exploring shadowing in tagged DIS on deuterium at x << 0.1. The JLab MEIC design (CM energy sqrt{s} = 15-50 GeV/nucleon, luminosity ~ 10^{34} cm^{-2} s^{-1}) provides polarized deuterium beams and excellent coverage and resolution for forward spectator tagging. We summarize the physics topics, the detector and beam requirements for spectator tagging, and on-going R&D efforts.